Electrical transients, often called surges, are short-duration, microsecond events. Surges are a risk to any electrical equipment, and electric vehicle (EV) charging infrastructure is no exception. Such events can interrupt, delay, or corrupt signal transmissions. More significantly, they can damage, degrade, and destroy electronic equipment.
“A surge is unlike any other power quality anomaly out there in that a fuse or a breaker cannot react fast enough to stop a microsecond transient event,” explained Jason Mies, director of Industrial Sales with Raycap, a global electrical protection and connectivity solutions manufacturer. Mies presented at the 5th EV Charging Infrastructure Summit in Chicago, Illinois, this July. “This means specially designed equipment called Surge Protection Devices (SPD) that react in nanoseconds are required to divert that microsecond event to the ground and protect the downstream equipment.”
Consider the ac sine waves in Figure 1. The spikes are all transient events, which can damage or destroy equipment — immediately or over time.
Figure 1. A transient or surge event is a sudden and brief increase in voltage that can be quite intense — as shown in the ac sine waves.
“In terms of surges, we often hear about a lightning event completely damaging equipment. However, the real concern is the smaller surge events that can degrade electronics over time,” said Mies. “Let’s take an EV charger expected to perform for 10, 20, or even 30 years. Faulty power from to a switching transient could slowly degrade that charger over time, reducing its output and total life expectancy.”
EV charging infrastructure is already subject to numerous challenges, including network availability, charging speed, vehicle compatibility, O&M concerns, and others. The reliability of the power source related to a surge event is one concern no EV driver should have to add to this list.
“If a driver pulls up to a charger and it’s out of service due to a surge event, that’s one thing that could have easily been prevented,” he said. “While equipment immunity to surges varies, it typically requires external surge protection to ensure reliability for the intended useful life. Installing surge protection in front of the charger is undoubtedly a best practice.”
Mies added that Europe already requires surge protection in three separate locations in an EV charging site to comply with the International Electrotechnical Commission (IEC), the international standards organization for electrical, electronic, and related technologies. However, this is not yet the case in the United States. Until it becomes standard regulation, it’s up to OEMs and installers to ensure the safest, most reliable infrastructure possible.
What’s the difference between a surge and an over-voltage event?
A power surge is a brief and sudden increase in voltage that lasts only a few microseconds. According to the Institute of Electrical and Electronics Engineers (IEEE), it’s a transient event that’s an 8×20 waveform (Figure 2). The IEEE is currently the world’s largest professional association for electronics and electrical engineering.
An over-voltage, on the other hand, occurs when the voltage exceeds the normal range for a more extended period, potentially causing overheating and damage to electrical equipment. Essentially, surges are microsecond events, whereas over-voltages are fault events that can last for seconds, minutes, or hours.
Figure 2. A surge event is a sudden, short spike in voltage lasting from microseconds to milliseconds (left), whereas an overvoltage is a sustained increase in voltage, lasting from seconds to hours (right).
It’s important to install proper fuses and breakers to protect equipment from over-voltages and install surge protection for surges. Why? Because these devices react in nanoseconds to protect against that microsecond transient event, according to Mies.
“It could cost thousands of dollars in damaged equipment, not to mention downtime and service required, thanks to an electrical surge,” he warned. “Prevention is simple… if you want to keep your site up and running and reliable, surge protection is a very inexpensive way to eliminate many of the headaches and hazards related to surge events.”
Where should surge protection be installed in EV chargers?
Surge protection should be strategically installed to ensure comprehensive protection for the EV charging equipment and the connected vehicle. The most significant place to protect against a lightning or utility fault event is at the power distribution panel, which feeds the charger.
“You might think the OEM or charging companies will take care of installing surge protection at the factory, but if that protection is sacrificed, it’s necessary to replace the full charger,” said Mies. “So, placing this protection in the power distribution cabinet better safeguards all the downstream charging equipment.”
The amount of exposure is also a factor, he added, as big utility lines can conduct a lot of energy, making installing SPDs at the equipment supplying power to the chargers the ideal location.
Figure 3. Ideally, all equipment powered by an external source of electricity should be protected from surges, and EV charging infrastructure is no exception.
In the case of a major power event related to a downed power line or transformer damage, it’s ideal to have surge protection that’s rated to protect against fault events at that power distribution equipment. In this case, it’s protecting the equipment and the power service.
Another threat to chargers relates to unbonded ground systems when there’s already existing power. “We call this ground potential rise,” he shared. “It happens at sites with ground systems that are not connected. If lightning strikes, it dissipates through the earth and hits and energizes the ground systems for the equipment at different levels. The power and signal conductors will try to equalize the energy between the equipment, causing damage.”
This means surge protection is required at the opposite ends of each of those lines to protect the equipment properly.
When evaluating surge protection for an EV charging site, consider the following:
- At the voltage protection level, size the surge protection as close to the nominal voltage of the equipment as possible. “If it’s a 480-volt device charger, it’s important to use a 480-volt rated surge protector,” said Mies. “Ensure you’re clipping that energy as close to the nominal as possible.”
- Ensure the surge protection equipment complies with the latest UL 1449 standards (see the UL site for exact ratings based on the manufacturer and product). This ensures the device has been tested properly and can handle voltage events safely.
- Avoid cheaper designs to save costs. “If the surge protector is improperly designed, then it can cause smoke, and even fire at a site that’s completely avoidable. So, make sure you go on online and check that UL listing,” he said. “Most reputable surge protectors are designed to handle multiple events without needing to be serviced or swapped out.”
- The most important consideration is for a surge protector to sacrifice in safe mode if it reaches end-of-life.
Is it worth the cost?
“How much does an EV charger cost?” asked Mies. “An SPD is typically far less costly than a charger, and maybe 10% of the total cost. I’d say that’s worth the cost of service calls, downtime, and potential equipment damage. Overall, surge protection is an extremely inexpensive way to keep equipment running.”
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Filed Under: Charging, FAQs, Featured Contributions, Safety Systems